This invention relates generally to small bend-forming tools, and more particularly to manually operable bender devices of the type especially adapted to impart any of a number of predetermined shapes to pieces of relatively thin metal stock.
In the past, numbers of tools for performing a variety of bending operations have been proposed and produced, and have met with varying degrees of success.
One such prior construction is shown and described in U.S. Pat. No. 3,901,064 dated Aug. 26, 1975. The device disclosed therein involves a bender apparatus having a handle which can swivel about a pivotal axis on a base, a bend-forming die, and a vise having two jaws, one of which is movable and the other of which is fixed. While this patented device has been found to perform in a generally acceptable manner, it has several limitations, particularly as far as ease of operation is concerned when it is desired to perform certain specialized bending operations quickly, such as those involving the formation of elliptical or modified cylindrical shapes for bracelets, jewelry and the like.
In particular, in the patented device the work-engaging shoulder on the handle was constituted as an upstanding pin which was restricted to movement with the handle along a path of constant radius about the pivotal axis. As clearly illustrated in FIG. 7 of the patent, this pin was disposed a substantial distance from the die; as a result, the overall length of the stock had to be sufficient to insure its continued engagement with the pin during the bend forming process, with any excess material usually being trimmed off after the bend was fully completed. This resulted in considerable additional expense, due to the extra operations involved. Also, where gold or silver articles such as bracelets were being formed, the value of the stock was such that it was uneconomical to merely discard the trimmed off material.
In cases where a die having an irregular shape was being employed, difficulty was often encountered in completing the last phase of the bend, since the location of the shoulder or pin on the handle was such that it was unable to guide and follow the metal at its free end. Accordingly, after a certain point in the bend-forming procedure was reached, the clamp was loosened and the metal stock re-positioned with respect to the shoulder of the handle. Such re-positioning of the stock represented an additional step in the manufacture of the item, sometimes adding significantly to the overall cost thereof.
Where resilient metals having a high degree of springiness were being formed, there was a pronounced tendency for the metal to return somewhat toward its original shape after the handle was backed off. Accordingly, with springy materials the bending operation tended to be more difficult and time-consuming.
Another disadvantage of the prior art device was that the steps of clamping the workpiece in a first position and thereafter re-positioning it as necessary proved to be time-consuming, especially where a large number of individual parts was being processed. Although the disclosed arrangement was satisfactory from the standpoint of adequately clamping the parts and holding them in a stationary position, the time and effort involved in manual operation of the vise proved to be excessive, and this constituted an obstacle to the rapid completion of jobs.